Efficient H 2 Production from Ethanol over Mo 2 C/C Nanotube Catalyst
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Efficient H2 Production from Ethanol over Mo2C/C Nanotube Catalyst R. Barthos Æ A. Sze´chenyi Æ F. Solymosi
Received: 10 August 2007 / Accepted: 1 September 2007 / Published online: 20 September 2007 Springer Science+Business Media, LLC 2007
Abstract Mo2C deposited on silica is an effective catalyst for the decomposition of ethanol; the extent of the reaction approached 100% even at 623–673 K. Beside H2 several C-containing compounds were produced, which caused the low yield of hydrogen. Preparation of Mo2C by the reaction of MoO3 with multiwall carbon nanotube, however, dramatically altered the product distribution. The formation of hydrogen came into prominence; about 40% of hydrogen content of ethanol decomposed at 523–723 K has been converted into H2. Another feature of the Mo2C/C nanotube is the relatively slow deactivation. Adding water to ethanol further enhanced the hydrogen production. Keywords Hydrogen production Ethanol decomposition Mo2C catalyst Multiwall carbon nanotube as a support
1 Introduction The production of hydrogen from alcohol, particularly from bioethanol gained an increasing attention in recent years [1–13]. Al2O3-supported noble metals are effective catalysts for the decomposition of ethanol, but the elimination of large amount of CO formed needed the use of gas mixture of ethanol + H2O. Even in this case the reaction is operated at high temperatures around 973 K. Another drawback is the rapid deactivation of the catalysts very likely due to the deposition of strongly bonded acetate [14,
15]. In the light of these features, great efforts are being made: (i) to replace Pt metals with less expensive catalysts, (ii) to lower the reaction temperature, and (iii) to increase the stability of the catalyst. Recently we found that the combination of Mo2C with ZSM-5, which exhibited a unique catalytic performance in the direct conversion of methane and other alkanes into benzene [16–27], is an excellent catalyst for the aromatization of ethanol, too [28, 29]. High yield of aromatics (toluene, xylenes and benzene in decreasing selectivity) was obtained at 773–873 K. In this very complex process; beside the activation of ethanol, two reactions seemed important: the dehydration of ethanol to ethylene, and its subsequent dehydrocyclization to aromatics. In both processes the Bro¨nsted acidic sites of ZSM-5 played an important role. The formation of H2 was also registered during the reaction, but due to the production of several H-containing compounds (aromatics and other hydrocarbons) its amount was very low. As will be demonstrated in this work the reaction pathway of ethanol can be dramatically altered, and the production of H2 can be markedly enhanced by applying multiwall carbon nanotube as a support, which do not contain Bro¨nsted sites important for the aromatization processes. The catalytic performance of Mo2C/C nanotube is comparable with that of supported Pt metals.
2 Experimental 2.1 Methods
R. Barthos A. Sze´chenyi F. Solymosi (&) Institute of Solid State and Radiochemistry,
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